Determinants of impaired memory and related cognitive functions are different in alcohol amnestic disorder patients (AMD), affective disorder patients (depression), panic disorder, early and middle stage Alzheimer~s disease (AD) patients, and in elderly normal controls. Patients with alcohol amnestic disorder (AMD) appear to demonstrate selective impairments in memory that requires subjects to be aware of the source of their memory and cognitive control functions (meta-cognitive operations necessary for judging and predicting the quality of one's own cognitive performance) but not for memory that is part of knowledge in long term memory or for memory that is reflected in performance where subjects need not be aware of the source of their memory. This failure in explcit memory may be important in maintaining craving and patterns of alcohol abuse. Impairments in frontal lobe functions may determine some of the cognitive change induced by the acute and chronic effects of alcohol. In contrast, AD patients demonstrate impaired recent memory that is directly tied to their inability to make use of their knowledge base for encoding and organizing their experience. This feature of AD impaired cognitive functioning may prove to be both a sensitive but also a specific early symptom of this disease. How memory fails in different populations of cognitively impaired nueopsychiatric patients provides an important framework for defining the mechanisms of acquisition, retention, consolidation and retrieval functions that are important defines memory.